I strongly suspect that he knows a lot more about words than you or I are ever likely to.

And that really seems to threaten many people for some reason. Can't say as I understand the phenomenon, myself. I'd never dream of expecting other people's vocabularies to my conform to my own personal, preferred lexicon. Nor would I immediately assume that an author who uses words that aren't a part of my own vocabulary must be trying to "impress" someone.